Control of isometric force in hypergravity.
BACKGROUND
Previous work suggests that proprioceptive signals are degraded in hypergravity (hyper-G). We therefore, expected that production of finely graded force is disturbed as well.


METHODS
Subjects produced isometric force with their thumb and index finger upon verbal instruction, before, during and after exposure to +1.5 Gz and +3 Gz. Produced force was orthogonal to the direction of gravity.


RESULTS
In hyper-G, responses to a given target value were significantly higher (by about 400 pond) than in normal gravity, while the modulation of produced force with target force didn't change. The results in +1.5 Gz and +3 Gz were quantitatively similar, and a positive aftereffect was found.


CONCLUSIONS
Subjects underestimate by a constant amount the force they produce in hyper-G. Our results are reminiscent of similar findings with pointing and grasping movements in hyper-G.
Bock
O
O
German Sports University, Köln, Germany.
Cheung
B S
BS
D000328:Adult; D000704:Analysis of Variance; D002498:Centrifugation / Q000009:adverse effects*; D005260:Female; D006801:Humans; D018471:Hypergravity / Q000009:adverse effects*; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D011434:Proprioception / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D013997:Time Factors